The present invention relates to an image information processinq apparatus, such as an electronic filing apparatus which stores a vast amount of image information and performs retrieval or edition of the stored image information.
Recently, an electronic filing apparatus has been developed for use as an image information processing apparatus to process a vast amount of image information such as documents. This electronic filing apparatus reads a vast amount of such image information by means of optical, two-dimensional scanning, sequentially stores the image information on, for example, an optical disk, and stores retrieval data for each item of the image information on, for example, a magnetic disk. When the retrieval data is entered, the electronic filing apparatus retrieves the image information stored in the optical disk and provides a visual output of the information, by means of an output device such as a cathode ray tube display device (hereinafter referred to as CRT display device) or a recording device. Furthermore, this type of filing apparatus can be applied to a system that comprises a plurality of terminals for inputting, retrieving, and editing image information, all of which are coupled on-line to an electronic filing apparatus (host machine), which stores all the image information processed by the terminals, or to a system in which host machines located in separate departments are coupled on-line to one another, so that one host machine can retrieve image information stored in another machine when needed.
However, the pixel density of image information processed by such host machines is limited. Conventional terminals and electronic filing apparatuses are coupled to input/output devices for image information, such as a scanner, a facsimile machine, and a printer, which have a pixel density (or resolution) of 8 pixels/mm.times.7.7 pixels/mm (main-scanning direction.times.sub-scanning direction) or 18 pixels/mm.times.15.4 pixels/mm (mainscanning direction.times.sub-scanning direction). Therefore, the electronic filing apparatus is designed to process only image information with 8 pixels/mm.times.7.7 pixels/mm or 16 pixels/mm.times.15.4 pixels/mm, which matches the pixel density of the input/output devices.
Some recent electronic filing apparatus, however, are designed to be coupled to input/output devices having a pixel density different from that of conventional devices, in order to process image information with new pixel densities. Accordingly, image information may have various types of pixel densities: they may be reproduced in the form of pixels/mm or pixels/inch, or may differ in the number of pixels per mm or inch, for example, 8 pixels/mm, 16 pixels/mm, 200 pixels/inch, or 400 pixels/inch. Therefore, it is likely that image information with different pixel densities are transferred between input/output devices with different pixel densities. This may happen when electronic filing apparatuses storing image information with a conventional pixel density are coupled on-line to those storing image information with a new pixel density via a LAN (local area network) to provide information retrieval between these apparatuses, or when image information stored in an optical disk with one pixel density is retrieved by another apparatus with a different pixel density.
Suppose that a apparatus which stores image information with a pixel density of 8 pixels/mm.times.7.7 pixels/mm is coupled on-line to another apparatus which stores image information with a pixel density of 200 pixels/inch.times.200 pixels/inch. When the image information stored in the former apparatus is retrieved by the latter apparatus, the output image information differs from the original (proper) image information, and is deformed such that the output image information has a reduced size for the main-scanning direction and a increased size for the sub-scanning direction in comparison to the original.
When image information stored in an optical disk with a pixel density of 200 pixels/inch.times.200 pixels/inch is retrieved by an apparatus that stores image information with a pixel density of 8 pixels/mm.times.7.7 pixels/mm, the output image information differs from the original (proper) image information and is distorted such that the output image information has an increased size, with respect to the main-scanning direction, and a reduced size, with respect to the sub-scanning direction, in comparison to the original. Further, when an apparatus that is correctly displaying image information (destination pasting image) with a pixel density of, for example, 400 pixels/inch.times.400 pixels/inch retrieves image information (source image) with a pixel density of 16 pixels/mm.times.15.4 pixels/mm and when the source information is pasted on the destination pasting image, the image information to be pasted (the source image) would be distorted on the destination pasting image.
Obviously therefore, when retrieval of image information with different pixel densities is executed by means of the prior art, the original or source image information cannot be accurately reproduced.